This name has been used in the Netherlands since medieval times. It was originally a shorter form or variant of Nicolaes, which is the (late) medieval form of the modern Dutch name Nicolaas. The English equivalent of that name is Nicholas, of course.

Nicol was exclusively a masculine name at the time, but the name has since become used on females as well. That happened in the second half of the 20th century, after World War II. In the women's case, the name is a variant spelling of the French given name Nicole, which was rising in popularity in the Netherlands at the time.

Nowadays, on a total population of about 16.9 million people, the name can be considered rare for both genders. Out of the two, it is rarest on the males: there were 40 male bearers in 2014 versus 436 female bearers that year.

Here are some useful links that are worth a look (with the help of Google Translator, if necessary):